Process for nickel and chromium plating

ABSTRACT

IN A PROCESS FOR SUBJECTING AN ARTICLE TO BRIGHT NICKEL PLATING AND SUBSEQUENTLY TO CHROMIUM PLATING, THE IMPROVEMENT IN WHICH THE BATH FOR SAID BRIGHT NICKEL PLATING CONTAINS A WATER-SOLUBLE QUATERNAIRIZED POLYMER OF AT LEAST ONE OF VINYL PYRIDINES, VINYL QUINOLINES AND AMINO STYRENES.

United States Patent O1 hoe 3,758,389 Patented Sept. 11, 1973 3,758,389 PROCESS FOR NICKEL AND CHROMIUM PLATING Hiroshi Maekawa, Sakai, Japan, assignor to Okuno Chemical Industry Company Limited, Osaka-shi, Japan No Drawing. Filed Nov. 30, 1971, Ser. No. 203,422 Int. C1. (123]: 5/08, 5/46, 5/50 US. Cl. 204-41 11 Claims ABSTRACT OF THE DISCLOSURE In a process for subjecting an article to bright nickel plating and subsequently to chromium plating, the improvement in which the bath for said bright nickel plating contains a water-soluble quaternarized polymer of at least one of vinyl pyridines, vinyl quinolines and amino styrenes.

The present invention relates to a process for nickel and chromium plating, more particularly to a novel and useful process for nickel and chromium plating capable of forming coatings having high resistance to corrosion.

Various processes have heretofore been proposed for imparting improved corrosion resistance to nickeland chromium-coated metals such as steel, copper, zinc, aluminium, magnesium and alloys of these metals which are subject to corrosion. Further with plated plastic articles now extensively used as various parts in electronics and automotive industries, attempts have also been made to improve the anticorrosive properties of the plated articles since rust or verdigris is produced in the underlying copper coating deposited on the substrate, although the substrate, plastic material, per se is free from corrosion.

'In order to improve anticorrosive properties, a process has been known which comprises forming an article to be plated with a semibright plated coating containing less than 0.005% of sulfur and then subjecting the resulting article to bright plating to form a coating having a sulfur content of about 0.02 to 0.07%. Further in accordance with another process already known in the art, a nickel layer with a high sulfur content of 0.1 to 0.3% is provided between the underlying semibright coating and the upper bright coating formed in the above-mentioned process. Although these processes ensure high corrosion resistance, chromium plating for forming a finishing layer has to be carried out with ingenuity if sufficiently high order of anticorrosive properties are to be achieved. For this purpose, it is proposed to add a selenium compound or fluoride to the chromium plating bath to deposit micro-crack chromium coating so as to minutely distribute corrosive current resulting from local cell action and thereby obtain improved corrosion resistance. Further, it has also been proposed to form a bright nickel plated article with a nickel plated coating of about 1 to 3p on a bright nickel coating prior to the above chromium coating, using a nickel plating bath dispersed with an insoluble fine powder, for example, of silcia, barium sulfate, ferrocyanides, etc., to deposit the insoluble powder on the initial coating along with nickel.

However, these processes have limitations on their practice because of restricted plating procedures and troublesome steps and high skill required for operation. In the case of micro-crack chromium plating, for instance, the temperature and current density employed are limited to narrow range, with the amount of additives also limited to a narrow range, if cracks are to be obtained with uniformity. Moreover, micro-crack chromium plating requires a period of 8 to 10 minutes with application of current of 30 a./dm. on average, while conventional chromium plating can be satisfactorily carried out generally within 1 to 3 minutes under the same conditions,

hence uneconomical from the view point of equipment and cost. The nickel plating process employing a dispersion of insoluble fine particles is also disadvantageous in that current has to be applied at a density of limited range and that agitating the bath requires high skill. Further, if the amount of the fine particle deposited along with nickel is small, resistance to corrosion will be markedly deteriorated. Thus the above processes need excellent skill and technique in practical application, with the result that in spite of high corrosion resistance achieved by these processes, they are not widely employed at present.

A primary object of this invention is to eliminate such drawbacks encountered with conventional processes and to provide a process of nickel and chromium plating capable of forming plated coatings having high resistance to corrosion with simple procedures.

The present invention provides a process for subjecting an article to bright nickel plating and subsequently to chromium plating which is characterized in that the bath for said bright nickel plating contains a water-soluble quaternarized polymer of at least one monomer selected from the group consisting of those having the formulas of \N/CH=CH1 (I) wherein R is hydrogen or an alkyl of l to 3 carbon wherein R is the same as defined above and n is 0 or an integer of 1 to 3.

In accordance with the researches of the present inventors, it has been found that when bright nickel plating is conducted in the presence of the above specific watersoluble polymer with subsequent chromium plating conducted in usual manner a highly anticorrosive plated layer is formed. In accordance with this invention, plating is conducted under the same conditions as with conventional bright nickel plating without using any special technique and apparatus, and highly anticorrosive plated layers can be formed with high efiiciency.

The monomers which constitue the polymers used in the invention are those having the above Formulas I to IH. Examples of the monomer (1) above are Z-methyl- 5-vinyl pyridine, 2-ethyl-5-vinyl pyridine, 2-propyl-5-vinyl pyridine, fl-vinyl pyridine, l-vinyl-2-methyl pyridine, lvinyl-2-ethyl pyridine, 1-vinyl-2-propyl pyridine and the like. Of these Z-methyl-S-vinyl pyridine is particularly preferable. The monomer (2) above includes, for example, l-vinyl quinoline 1-vinyl-2-methyl quinoline, l-vinyl-Z- ethyl quinoline, 1vinyl-2-propyl quinoline, l-vinyl-S- methyl quinoline, l-vinyl-S-ethyl quinoline, 'l-vinyl-S- propyl quinoline and the like, especially preferable being l-vinyl quinoline. Examples of the monomer (3) above are Z-dimethylamino styrene, Z-diethylamino styrene, 2- dipropylamino styrene, dimethylaminopropyl styrene and the like, particularly preferable being Z-dimethylamino styrene.

The water-soluble quaternarized polymers to be used in accordance with this invention are those prepared by quaternarizing the polymers of the foregoing monomers (1) to (3) so as to impart water-solubility to the polymers. The polymers of the monomers (1) to (3) include homopolymers of the respective monomers 1) to (3), copolymers of at least two of the monomers (1) to (3), and copolymers of at least one of the monomers (1) to (3) with other vinyl monomers especially with acrylomtrile. The copolymer with vinyl monomer should contain at least wt. percent, preferably at least 50 wt. percent, of at least one of the monomers (1) to (3). The polymers to be used in this invention are generally those having an average molecular weight of 5,000 to 100,000. Preferably, they should have a relative viscosity in a 1 wt. percent dimethyl formamide solution of 0.1 to 0.85 at 25 C.

The polymers per se are not water-soluble but are rendered water-soluble by quaternarization, which may be effected in usual manner, for instance, by using quaternarizing agent such as methyl sulfate, dimethyl sulfate,

ethyl sulfate, diethyl sulfate, allyl halide, alkyl halide,

propane sultone, etc. Quaternarization is generally conducted under reflux conditions in a solvent. The solvents used include, for example, lower alcohols such as methanol, ethanol, propanol-Z, etc., ketones such as acetone, methyl ethyl ketone, etc. and hydrocarbons such as benzene toluene, etc. The solvents may be used alone or in admixture with one another. By the quaternarization the polymer is rendered water-soluble. It is preferable to quaternarize 10 to 100%, particularly at least 30%, of the nitrogen atoms in pyridine or quinoline ring or amino group within the polymer molecules.

With the present invention, plating is conducted under the conditions generally employed for bright nickel plating, using a usual bright nickel plating bath containing the above-mentioned water-soluble quaternarized polymer added thereto. The quaternarized polymer is added to the conventional Watt bath preferably in an amount of about 0.01 to 0.5 g./liter, most preferably 0.05 to 0.3 g./liter. The composition of the Watt bath is the same as with usual process. For example the following composition generally employed may be used also in this invention.

-G./liter Nickel sulfate 150-350 Nickel chloride l00 40O Boric acid 20-90 The Watt bath may further contain a primary brightening agent and a secondary brightening agent as in usual process. The primary brightening agent to be used in this invention may be any of those already known, such as sulfonic acids like naphthalenesulfonic acid, saccharin and the like, and derivatives of sulfamide. Exemplary of the secondary brightening agent are those already known, such as (1) 2-butyne-1,4-diol, propargylalcohol, 2-butyne- 1,4-diethanedisulfonic acid, ester of 2-butyne-1,4-diol with sulfuric acid and the like acetylene compounds; (2) ethylenecyanohydrin, saccinonitrile, cyanoethyl thiohydantoin, bis-(,B-cyanoethyl) sulfone and the like nitrile compounds; and (3) N-allyl quinalidinium bromide, ethylenebis-[N-allyl(4)-formyl-pyridinium(2)bromide], N w-Slllfopropylpyrid-ine, N methylpyridinium sulfate and the like quaternary ammonium salts. The amount of the primary and secondary brightening agents used may vary over a wide range, but it is preferable to use the primary brightening agents in an amount of 0.5 to 3 g./liter and the secondary brightening agents in an amount of 0.05 to 0.2 g./liter.

The articles to be plated in accordance with the present invention include various products made of metals such as iron, copper, brass, etc. and resins such as acrylonitrile-butadiene-styrene copolymer, acrylonitrile styrene copolymer, polycarbonate, poly amide, polypropylene, polystyrene, etc.

The present bright nickel plating can be carried out on the articles subjected to the conventional preliminary plating as in the case of the usual bright nickel plating. For instance the metal products are subjected to the present bright nickel plating after the conventional semibright nickel plating or copper plating and the resin product are subjected to the present bright nickel plating after chemical copper plating and subsequent semibright nickel plating or copper plating.

In accordance with the present invention bright nickel plating may be conducted in conventional manner, for example, at a current density of 1-10 a./dm. at a temperature of 45 to 60 C. while agitating the system with air.

The article'coated with the present bright nickel plating is then subjected to conventional chromium plating, whereby plating layer having excellent corrosive resistance is formed on the resultant article. For the chromium plating a conventional Sergeant bath is used. One of the preferred examples of the bath is as follows:

G./liter Chromic anhydride 250 Sulfuric acid 2.5 Trivalent Cr ion 3 The chromium plating may be conducted, for example, at a current density of 20 a./dm. for 1 to 3 minutes. For a better understanding of the invention, examples are given below:

EXAMPLE 1 Preparation of quaternarized polymer 300 g. of 2-methyl-5-vinyl pyridine was mixed with 750 ml. of water containing 0.5 wt. percent of starch and the mixture was heated with stirring to 55 C. At that temperrature 100 ml. of 10 wt. percent aqueous solution of KQSZOB was added dropwise to the mixture. Thereafter the system was heated with stirring at C. for 4 hours to produce polymer of Z-methyl-S-vinyl pyridine having a number average molecular weight of 20,000 to 30,000 and a relative viscosity of 0.3 to 0.85 in 1 wt. percent dimethylformamide solution at 25 C.

To 20 g. of the resultant polymer dissolved in 150 ml. of water was added 20 g. of allyl bromide and the mixture was heated at 4050 C. for 3 hours, whereby watersoluble quaternalized polymer was obtained in the form of aqueous solution.

Plating on steel plate A steel plate, 0.8 mm. x 50 mm. x mm., was immersed in the following bath for semibright nickel plating at current density of 3 a./dm. at 50 C. to produce a semibright nickel coating of 14 in thickness.

Semibright nickel plating bath used:

Nickel sulfate g./liter 300 Nickel chloride do 50 Boric acid do 40 37 wt. percent formalin m1./liter 0.4 Coumarin g./liter 0.05 Lauryl sulfate do 0.005

Water, amount necessary for making one liter bath.

The resultant steel plate was then immersed in the prescut bright nickel plating bath shown below at current density of 3 a./dm. at 50 -C. to produce a bright nickel coating of 6 in thickness.

Water, amount necessary for making one liter bath.

The plate thus treated was thereafter immersed for chromium plating in the following Sergeant bath at current dinsitv of 20 a. /dm.f at 50 Ctilfoli 1 minute to pro- Bright nickel plating bath used: Gjliter duce c romium coatlngo 0.25 i in 1c ness. Nickel sulfate 240 Chromium plating bath used: G./liter 5 Nickel chloride 45 Chromic anhydride 250 Boric acid 40 Sulfuric acid 2.5 Allyl sulfonate 0.5 Trivalent chromium ion 2.0 Saccharin 1 Z-butynoxy-l 4-di(propyl sulfonic acid) 0.1

b t th fii g gz g gi plate thus obtained was Su lee ed to e Quaternarlzed polymer obtained abov 0.1

Water, amount necessary for making 1 liter (1) Cass test conducted in the manner disclosed in JIS bath (2) Corrodekote test conducted in the manner disclosed T eieafter the P1ate i treated was lmmersed the in HS DOZOL following chromlum plating bath at current density of (3) EC test conducted in the manner described in (kn-2 at 9 for 1 mmute to form chromlum Plating, vol. 53, No. 9, 1124 (1966). coatmg Of 015! In thlckness- The results of the tests are shown in the following Chromium P f bath used: G-Aiter Tables 1 to 3, which also show for comparison the test 20 Chrn 11c q 250 results on a steel plate plated in the same manner as sulfPnc E 9 15 above, except that bright nickel plating bath to which 502mm slhcofiuonde 5 the quaternarized polymer was not added was employed Cr 1 for bright nickel platlng. For comparison steel plate was plated in the same manner as above except that quaternarized polymer was not TABLE 1- CAsS TEST IN RATING NUMBER added to the bright nickel plating bath. Cycle 1 a 6 9 The test results conducted on the plated steel plates are comparison 5 5 M M shown in Tables 4 and 5 below. Example 1 10 TABLE 4.-CASS TEST IN RATING NUMBER Cycle 1 2 3 4 5 TABLE 2.CORROS1ON 1N PERCENT Comparison 6.0 5.5 4.8 4.0 3.5 Cycle 1 3 5 7 Example 2 10 10 9. 5 9. 0 8. 5

Comparison. 0. 8 1. 6 2. 4 3. 6 Examplel M M TABLE 5.CORROSION IN PERCENT Cycle 1 2 3 4 6 TABLE 3-EC TEST Comparison 5 10 20 60 Lapse of time when iron begins to dissolve out due to Examplez 0 0 electrolysis under constant potential 40 EXAMPLE 3 Seconds P f t d 1 Comparison 120480 reparatlon o qua ernarize p0 ymer Ex. 1 290-380 20 g. of Z-methyl-S-vinyl pyridine polymer obtained in the same manner as in Example 1 was dissolved in 100 EXAMPLE 2 ml. of acetone, to which 20 g. of propanesultone was Preparation of quaternarized polymer added dropwise. The system was heated with stirring at 15 g of benzoyl peroxide was added to 300 of 4050 C. for 30 minutes to obtain water-soluble quaterwater in nitrogen gas stream, to which were further added nanzed Polymer 20 g. of acrylonitrile and 80 g. of Z-methyl-S-vinyl pyri- Plating on ABS resin it:it srizlyrsfrssiiaiiuntiriidsriizasz o x x mm. was immerse in a mixture o 5 22 3 2233 63 5 2ggg ig giggggg iigzgi 22 g./ liter of chromic acid and 460 g./ liter of sulfuric acid 5,, C T p y g thus Obtaineg was dissolved in etha at 60 C. for 10 minutes. The plate was then washed with 1101 and 20 g. of methyl iodide was added to the solution. and further lmmirsed the i comPnSmg 15 The mixture was heated with Stirring at 40 to 50 C for g./llter of stannous chloride and 15 ml./llter of 35 wt. per- 4 h h 6b atepsoluble uatemarimd o1 cent hydrochloric acld at room temperature for 3 minutes.

g y w q p y Thereafter, the plate was immersed in the bath contalning was tame 0.2 g./1iter. of palladium chloride and 0.1 mL/Iiter of 37 Plating on steel plate wt percent hydrochloric acid at room temperature for 1 The steel ate, 0.8 mm. X 50 mm. x 100 mm., was immmute' mersed in thia following bright copper plating bath at cur- The resultmg .resm plate was Immersed at room i rent density of 3 a /dm 2 in periodic reverse method at ture for 3 m felectroless i zg i bat};

o k comprising g. iter 0 copper su ate, g. iter o 2 Pmduce bnght mung Rochelle salt, 20 g./liter of caustic soda and 30 ml./liter of 37 wt. percent formalin to form the copper coating of Bright PP Platlng bath used; 6/1061" about 0.3g in thickness on the surface of the resin plate.

Copper cyanide 30 The resin plate thus obtained was plated in acid copper Sodium cyanide 5 bath comprising 220 g./liter of copper sulfate, 50 g./liter Caustic potash 10 of sulfuric acid and 2 ml./liter of brightening agent at a Lead 10H current density of 3 a./dm. at 25 C. to form a coating Warez-1,1 amount necessary for making 1 liter of averagethickness f 20% The plate thus obtained was then immersed in the following bright nickel plating bath at current density of ABS resin plate thus obtained was subjected to bright nickel plating in the same manner as in Example 1 except that the quaternarized polymer obtained above was used TABLE 6.CASS TEST Cycle 1 3 Comparison 5. Example 3 10 9.0

EXAMPLE 4 Five steel plates were respectively plated in the same manner as in Example 1, except that the following kinds of quaternarized polymers were respectively used in an amount of 0.1 g./liter in bright nickel plating bath.

Quaternarized polymer used (A) Quaternarized polymer prepared by quaternarizing polymer of fl-vinyl pyridine having a number average molecular weight of 10,000 to 40,000 with allyl bromide in the same manner as in Example 2.

(B) Quaternarized polymer prepared by quarternarizing polymer of l-vinyl quinoline having a number average molecular weight of 30,000 to 40,000 with dimethyl sulfate in the same manner as in Example 2.

(C) Quaternarized polymer prepared by quarternarizing polymer of 1-vinyl-5-propyl quinoline having a number average molecular weight of 30,000 to 40,000 with dimethyl sulfate in the same manner as in Example 2.

(D) Quaternarized polymer prepared by quaternarizing polymer of 2-diethylaminostyrene having a number average molecular weight of 15,000 to 60,000 with allylbromide in the same manner as in Example 1.

(E) Quaternarized polymer prepared by quaternarizing polymer of 2-dimethylaminostyrene having a number average molecular weight of 10,000 to 30,000 with diethyl sulfate in the same manner as in Example 1.

The results of Cass Test conducted in the same manner as in Example 1 on each plate thus obtained are shown in Table 8 below.

TAB LE 8.CASS TEST wherein R is hydrogen or an alkyl of 1 to 3 carbon atoms,

H=CH wherein R is the same as defined above and /R (CH2) u wherein R is the same as defined above and n is 0 or an integer of 1 to 3, said polymer having an average molecular weight of 5,000 to 100,000.

2. The process according to claim 1, in which said quaternarized polymer is a Water-soluble quaternarized polymer of at least one monomer selected from the group consisting of those having the formula of CH=CH wherein R is hydrogen or an alkyl of 1 to 3 carbon atoms.

3. The process according to claim 2, in which said monomer is at least one member selected from the group consisting of 2-methyl-5-vinyl pyridine, 2-ethyl-5-vinyl pyridine, 2-propyl-5-vinyl pyridine, fi-vinyl pyridine, lvinyl-2-methyl pyridine, 1-vinyl-2-ethyl pyridine and 1-vinyl-2-propyl pyridine.

4. The process according to claim 3, in which said monomer is 2-methyl-5-vinyl pyridine.

5. The process according to claim 1, in which said quaternarized polymer is a water-soluble quaternarized polymer of at least one monomer having the formula of R I T OH=CH wherein R is hydrogen or an alkyl of 1 to 3 carbon atoms.

6. The process according to claim 5, in which said monomer is at least one member selected from the group consisting of l-vinyl quinoline, 1-vinyl-2-methyl quinoline, 1-vinyl-2-ethyl quinoline, 1-viny1-2-propyl quinoline, 1-vinyl-5-methyl quinoline, l-vinyl-S-ethyl quinoline and l-vinyl-S-propyl quinoline.

7. The process according to claim 6, in which said monomer is l-vinyl quinoline.

8. The process according to claim 1, in which said quaternarized polymer is a water-soluble quaternarized polymer of at least one monomer having the formula of (CI-Ia) DN wherein R is hydrogen or an alkyl of 1 to 3 carbon atoms and nis 0 or an integer of 1 to 3.

9. The process according to claim 8, in which said monomer is at least one member selected from the group consisting of Z-dimethylamino styrene, 2-diethylamino styrene, 2-dipropylamino styrene and dimethylaminopropyl styrene.

10. The process according to claim 9, in which said monomer is Z-dimethylamino styrene.

11. The process according to claim 1, in which said amount of water-soluble quaternarized polymer is in the range of 0.05 to 0.3 g./liter.

References Cited UNITED STATES PATENTS 3,054,733 9/1962 Heiling 204-49 3,170,853 2/1965 Kroll 204-49 GERALD L. KAPLAN, Primary Examiner U.S. Cl. X.R. 204 -DIG 2, 49 

